Many devices have been utilized in order to provide disinfectant or deodorant material for tanks, particularly toilet tank bowls, so that active material may be released into the toilet bowl during each flush and provide appropriate sanitary and environmental conditions in the area of the toilet bowl. The problem has always existed for determining when the material is used up without waiting for specific undesirable indications of the fact that the active material is gone. One method of providing such indication is to color the disinfectant material so that it in turn colors the toilet bowl water, thereby providing a permanent color indication of the fact that the disinfectant material is present. This discoloration of the toilet bowl water, however, is not always acceptable to the user and in fact depending on the attitude of the individual user, provides an indication of the utilization of disinfectant which the user may not desire. If, however, a disinfectant or deodorant which does not color the water is utilized, there is no dependable indication of the fact that the disinfectant is used up, such as occurs when the disinfectant constantly colors the water. In this case, the arrangement of a disinfectant or deodorant supply so that a visible indication is provided of the using up of the active material becomes important.
Various devices have been used in the prior art to provide such an indication at the container itself. Since, however, the container for disinfectant material is normally inserted in the tank, such indication is not a positive, readily available indication which the user can observe readily. Other devices have been utilized to provide signals of various types, but such signals have almost invariably been located at the container itself.